Gore Creek: Lower numbers for macroinvertebrates due to urbanization?

From the Vail Daily (Sarah Mausolf):

A recent study revealed certain bugs are disappearing in the East Vail stretch of the stream. The bugs present in low numbers — certain mayflies, stoneflies and caddisflies — are especially sensitive to the effects of urbanization, said David Rees, a bug expert processing the study data. And their absence is a sign that something is damaging this popular trout-fishing stream, which runs through a tourist town that prides itself on its natural beauty. “A large portion of our economy depends on this perception that this is a pristine area,” said Lin Brooks, assistant general manager for the Eagle River Water and Sanitation District.

Something has been causing a change in the stream’s macroinvertebrates, the tiny bugs that live in the rocks, Rees said. There are fewer types of bugs overall than one expects to see in a mountain stream, Rees said. While some bugs are dwindling, others are more plentiful then normal, he said. Midges and worms, which are less sensitive to environmental stress, are abundant. “Whenever we see this change in the composition, it’s an indication there’s stress,” he said…

John Woodling, a retired fish biologist familiar with the stream, agrees [highway] sand is a likely culprit. The sand settles over the rocks and fills up the space where the bugs live, he said. Although CDOT has been working to contain the sand, there is still plenty left on the hillside, he said…

Brooks said the water district plans to investigate other theories, too. One holds that fertilizers and lawn chemicals are hurting the creek…

Another theory claims road gunk that washes into the stream has been changing its makeup…

The state is coming up with new regulations for the nutrients wastewater treatment plants discharge, Brooks said. The water district volunteered to do the study to help explore the complex relationship between nutrients and river health, she said. Researchers collected samples at 18 locations along Gore Creek and the Eagle River in fall 2008 and spring 2009, Brooks said. They are still processing the results of samples they took in fall 2010, she said. Brooks expects The Colorado Water Quality Control Division to come out with new rules for nutrient discharge by June 2011. It could cost the water district $10 million to $20 million to remodel the local treatment plants to comply with the regulations, she said.

More Eagle River watershed coverage here and here.

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